Refrigerant charging system and method using vapor-phase refrigerant

ABSTRACT

A refrigerant charging system and method for charging a refrigeration system with a vapor-phase refrigerant includes a refrigerant source, an input line, a sensor and a pressure regulator. The input line connects the refrigerant source to the refrigeration system. One or more valves are disposed between the refrigerant source and refrigeration system to regulate the pressure of the refrigerant being introduced into the refrigeration system, and the sensor measures the pressure of the refrigerant entering the refrigeration system. A pressure regulator can also be used to regulator the flow of refrigerant. Once the pressure of the refrigerant reaches a predetermined pressure, the refrigeration system is fully charged, and the transfer of refrigerant to the refrigeration system is stopped. The system and method are used to charge the refrigeration system of, e.g., an automotive vehicle, and the refrigeration is carbon dioxide.

TECHNICAL FIELD

The disclosure relates generally to refrigerant charging systems and,more specifically, to a high precision, vibration-resistant refrigerantcharging system.

BACKGROUND ART

Most refrigeration systems are not 100% free of leaks. Thus, the amount(or mass) of refrigerant within the refrigeration system decreases overtime. Refrigeration systems, however, are designed to operate with aspecific amount of refrigerant. Therefore, loss of refrigerant in arefrigeration system over time typically reduces the efficiency of therefrigeration system. Also, if the amount of refrigerant in therefrigeration system drops to a certain level, the refrigeration systemmay cease to operate and/or be damaged. For these reasons, a commonmaintenance operation for a refrigeration system is to recharge therefrigerant within the refrigeration system.

The recharging operation typically involves flushing the refrigerationsystem of any remaining refrigerant and, if present, other materialswithin the refrigeration system. Once the refrigeration system isflushed, a predetermined amount of new refrigerant is introduced intothe refrigeration system. An important component of conventionalrefrigeration charging systems is the device that measures the amount ofrefrigerant introduced into the refrigeration system. Since therefrigeration system is designed to operate with a specific amount ofrefrigerant, too little or too much refrigerant can reduce theeffectiveness of the recharging operation.

One conventional device used to measure the amount of refrigerantintroduced into the refrigeration system is a load cell (or scale).Essentially, the load cell measures the weight of a tank containing therefrigerant before the refrigerant is introduced into the refrigerationsystem and then afterwards. The difference between the two readings isthe amount of refrigerant introduced into the refrigeration system.There are, however, certain problems that are associated with the use ofa load cell in conventional recharging systems. Load cells are sensitiveto vibration, which can throw off the measurements. Also, since the loadcell determines the weight of the entire tank used to supply therefrigerant, which can weigh several hundred pounds or more, sensitivityof the load cell is reduced.

The recharging of refrigeration systems has been complicated by thechanges in refrigeration systems and refrigerants used in therefrigeration systems. Recently, the refrigerant in automobile airconditioning systems has been switched from chlorofluorocarbon 12(CFC-12) to hydrofluorocarbon 134a (HFC-134a) for the purpose of ozonelayer protection. However, HFC-134a is considered to be a contributor toglobal warming, and new types of refrigerant are being considered, ofwhich carbon dioxide (CO₂) is one. Compared to HFC-134a, carbon dioxideonly has about 1/1300 the global warming potential. However, the use ofcarbon dioxide presents issues not seen with conventional refrigerationsystems. For example, carbon dioxide has an operation pressure that is 7to 10 times higher than that of HFC-134a. The resulting increase inpressure necessitates thicker walls for the equipment handling thecarbon dioxide, such as the storage tank for the refrigerationrecharging system. These thicker walls add additional weight to thetank, which further exacerbates the previously discussed problems, suchas the sensitivity of the load cell.

Another conventional device used to measure the amount of refrigerantintroduced into the refrigeration system employs mass flow technology.As recognized by those skilled in the art, mass flow technologyimplements a sensor that measures the flow rate of fluid (i.e., therefrigerant) flowing past a certain point. However, use of mass flowtechnology is very expensive, and the expense is even greater when anincreased sensitivity for calculating the amount of refrigerantdelivered is desired. The accuracy of mass flow technology is dependenton the fluid state since the mass flow sensor does not measure gas aswell as liquid. Although most refrigerants are in a liquid form duringthe recharging operation, carbon dioxide is in a gaseous state during arecharging operation. Also, mass flow technology does not work well withtwo-phase fluids. Thus, when carbon dioxide, or another gaseousrefrigerant, is used, the sensitivity of the mass flow technology isreduced. There is, therefore, a need for a refrigerant charging systemand method that is more accurate and vibration-resistant, and lessexpensive than conventional refrigeration charging systems, particularlywhen the refrigerant is a gaseous refrigerant such as carbon dioxide.

SUMMARY OF THE DISCLOSURE

Described is a system and method for charging a refrigeration systemwith a vapor-phase refrigerant. The charging system includes arefrigerant source, an input line, a sensor and a control valve. Theinput line connects the refrigerant source to the refrigeration system.The control valve regulates the flow and pressure of the refrigerantbeing introduced into the refrigeration system, and the pressure sensormeasures the pressure of the refrigerant entering the refrigerationsystem. Once the pressure of the refrigerant reaches a predeterminedpressure, the refrigeration system is fully charged, and the transfer ofrefrigerant to the refrigeration system is stopped. The refrigerant maybe a gaseous, such as carbon dioxide.

Additional advantages will become readily apparent to those skilled inthe art from the following detailed description, wherein only anexemplary embodiment of the present invention is shown and described,simply by way of illustration of the best mode contemplated for carryingout the present invention. As will be realized, the disclosure iscapable of other and different embodiments, and its several details arecapable of modifications in various obvious respects, all withoutdeparting from the invention. Accordingly, the drawings and descriptionare to be regarded as illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a refrigerant charging system, accordingto the disclosure; and

FIG. 2 is a flow chart of a method of charging a refrigeration system,according to the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An example of a refrigerant charging system 10 is illustrated in FIG. 1.The refrigerant charging system includes a refrigerant source 12, aninput line 16, a sensor 19 and a control valve 14 for controlling theflow of refrigerant from the refrigerant source 12 through the inputline 16. The input line 16 fluidly connects the refrigerant source 12 toa refrigeration system of the vehicle 32. The input line 16 may alsoinclude an exit control valve 20 for controlling the flow and pressureof refrigerant from the input line 16 to the refrigeration system of thevehicle 32. The refrigerant charging system 10 may include a pressureregulator 18 that is used in place of the control valve 20 to controlthe flow of refrigerant to the refrigeration system. Alternatively, thepressure regulator 18 may be used in addition to the exit control valve20.

The refrigerant source 12 is not limited as to a particular type ofsource for providing refrigerant. However, in a current aspect of therefrigerant charging system 10, the refrigerant source 12 is aconstant-volume tank.

The sensor 19 measures the pressure and/or temperature of therefrigerant being introduced into the refrigeration system, and thesensor 19 is not limited to a particular location. For example, thesensor may be located along the line 16 anywhere between the pressureregulator 18 and the refrigeration system. Alternatively, as illustratedin FIG. 1, the sensor 19 may be directly connected to the refrigerationsystem. The use of a sensor 19 to measure pressure and/or temperature ofa fluid within the refrigeration system, and the refrigerant chargingsystem 10 is not limited as to any particular type or configuration oftemperature and/or pressure sensor 19. The sensor 19 may also beconfigured to adjust a measured value of the pressure of the refrigerantbased upon a measured temperature of the refrigerant. For example, ifthe measured temperature of the refrigerant varies from a presetbaseline temperature, the sensor 19 may adjust the measured pressureupwards or downwards to indicate the pressure the refrigerant would beat if the refrigerant was measured at the baseline temperature.

Many different types of pressure regulators 18 exist that are capable ofregulating the pressure of a vapor-phase refrigerant, and therefrigerant charging system 10 is not limited to any particular type ofpressure regulator 18 so capable. A common pressure regulator 18includes a pressure adjustor 26 and a low-pressure-side gauge 24 thatrespectively adjusts and monitors the pressure of the refrigerantleaving the pressure regulator 18. The pressure regulator 18 may alsoinclude a high-pressure-side gauge 22 that indicates the pressure of therefrigerant entering the high-pressure-side of the pressure regulator,which in this case is the pressure of the refrigerant in the refrigerantsource 12. The pressure regulator 18 may include a safety-valve 30 thatactivates when pressure on the low-pressure-side of the pressureregulator 18 exceeds a certain predetermined pressure.

The refrigerant charging system 10 can optionally include a controller28 connected to the sensor 19, the pressure regulator 18 and/or thecontrol valves 14, 20. Although the control valves 14, 20 and pressureregulator 18 can be operated manually, the controller 28 may be used toautomatically control the operation of these devices. Additionally,information from the sensor 19 can be sent to the controller 28, eitherautomatically or manually, and the controller 28 may use thisinformation during the control of the control valves 14, 20 and thepressure regulator 18.

In an aspect of the refrigerant charging system 10, the refrigerant tobe introduced into the refrigeration system of the vehicle 32 is in avapor-phase during the recharging operation. An example of such arefrigerant is carbon dioxide. The pressure regulator 18 acts tomaintain the pressure downstream of the pressure regulator 18 to be nogreater than a particular predetermined pressure, which is based upon apressure of refrigerant in the refrigeration system needed to completelycharge the refrigeration system. Instead of determining when arefrigeration system has been charged based upon the amount ofrefrigerant by weight/mass introduced into the refrigeration system, aswas done with prior charging systems, the present refrigeration chargingsystem 10 charges the refrigeration system based upon the pressure ofthe refrigerant in the refrigeration system.

Since prior charging systems are used for liquid-phase refrigerants, apressure regulator was not used in these systems to determine the amountof refrigerant charged into the refrigeration system because thepressure regulator would not be capable of reliably determining thecorrect amount of refrigerant. At a given temperature, a liquidrefrigerant has a particular vapor pressure. Once the vapor pressure hasbeen met, no matter how much additional refrigerant is added, as long asthe temperature remains constant, the measured pressure (i.e., the vaporpressure) also remains constant. Therefore, the pressure of therefrigerant is not used in calculating the amount of liquid refrigerantadded because at a certain point, the measured pressure remains the sameeven while refrigerant is being added. In contrast, a refrigerant, suchas carbon dioxide, remains gaseous at operational temperature/pressurecombinations; and thus, the addition of refrigerant will increase thepressure of the refrigerant.

The operations of the refrigerant charging system 10 are schematicallyillustrated in the flow chart of FIG. 2. In an initial step 110, arequired pressure of refrigerant to be charged into the refrigerationsystem of the vehicle 32 is predetermined. Many techniques ofpredetermining the pressure of refrigerant to be introduced into arefrigeration system are well known in the art, and the presentmethodology of charging a refrigeration system is not limited to anyparticular technique. For example, after flushing the refrigerationsystem of any remaining refrigerant, which may involve discharging anyremaining refrigerant and pulling a vacuum within the refrigerationsystem, the pressure of the new refrigerant within the refrigerationsystem can be predefined for different temperatures by the manufacturerof the refrigeration system. The predetermined pressure is later usedfor comparing with a measured pressure of the refrigerant. Dependingupon where the pressure of the refrigerant is measured, thepredetermined pressure may vary from the pressure of the refrigerant inthe refrigeration system defined by the manufacturer of therefrigeration system.

In step 120, refrigerant is transferred from the refrigerant source 12to the refrigeration system of the vehicle 32, and the transfer of thisrefrigerant may be regulated using a pressure regulator 18 or the exitcontrol valve 14. For example, the pressure regulator 18 reduces thepressure of the refrigerant exiting the refrigerant source 12 to apressure compatible with the predetermined pressure. Alternatively, theoperation of the exit control valve 14 can be used to stop or allow flowof refrigerant into the refrigeration system.

After the flow of refrigerant into the refrigeration system has beeninitiated and regulated, in step 130, the pressure of the refrigerant ismeasured using a sensor 19, located, for example, between and includingthe refrigeration system and the pressure regulator 18 or exit controlvalve 14. In step 140, this measured pressure (adjusted for temperature)is compared to the predetermined pressure. When the measured pressureequals or exceeds the predetermined pressure, the flow of refrigerantfrom the refrigerant source 12 to the refrigeration system is stopped.

Through use of the present refrigerant charging system, refrigerant canbe charged into a refrigeration system with comparable or improvedaccuracy than prior technology used for the same purpose. Also, sincethe present refrigerant charging system can function without mass flowtechnology, the present refrigerant charging system is less expensivethan those systems that employ mass flow technology and has increasedaccuracy, such as with vapor-phase refrigerants (e.g., carbon dioxide).Furthermore, since the present refrigerant charging system does notemploy a load cell, the system is less sensitive to vibration, which hasbeen a source of inaccuracy with prior systems that employ a load cell.

The disclosed concepts may be practiced by employing conventionalmethodology and equipment. Accordingly, the details of such equipmentand methodology are not set forth herein in detail. In the previousdescriptions, numerous specific details are set forth, such as specificformulas, processes, techniques, etc., in order to provide a thoroughunderstanding of the present invention. However, it should be recognizedthat the present invention may be practiced without resorting to thedetails specifically set forth.

Only an exemplary aspect of the present disclosure and but a fewexamples of its versatility are shown and described. It is to beunderstood that the present invention is capable of use in various othercombinations and environments and is capable of changes or modificationswithin the scope of the inventive concept as expressed herein.

1. A refrigeration charging system for charging a refrigeration systemof a vehicle with a vapor-phase refrigerant, comprising: a refrigerantsource for storing the vapor-phase refrigerant; an input line connectedto the refrigerant source and configured to be connected to therefrigeration system of the vehicle; a sensor for detecting a pressureof the vapor-phase refrigerant being introduced into the refrigerationsystem of the vehicle from the input line; a control valve between therefrigerant source and the refrigeration system of the vehicle; acontroller connected to the control valve and the sensor, wherein duringa refrigeration charging operation, the controller is configured toclose the control valve directly responsive to a pressure of therefrigerant in the refrigeration system of the vehicle detected by thesensor reaching a predetermined pressure; a pressure regulator fluidlyconnected between the refrigeration system and the control valve, thepressure regulator connected to the controller, wherein the controlleris configured to adjust the pressure regulator for regulating thepressure of the vapor-phase refrigerant being introduced into therefrigeration system of the vehicle and set to a predetermined pressurecorresponding to a pressure of refrigerant needed to charge therefrigeration system; a high-pressure-side gauge for indicating pressureof the refrigerant entering a high-pressure-side of the pressureregulator; and a low-pressure-side gauge for adjusting and monitoringpressure of the refrigerant leaving the pressure regulator.
 2. Therefrigeration system according to claim 1, wherein the vapor-phaserefrigerant is carbon dioxide.
 3. A refrigeration charging system forcharging a refrigeration system of a vehicle with a vapor-phaserefrigerant, comprising: a refrigerant source for storing thevapor-phase carbon dioxide; an input line connected to the refrigerantsource and configured to be connected to the refrigeration system of thevehicle; a pressure regulator for regulating a pressure of thevapor-phase refrigerant being introduced into the refrigeration systemof the vehicle via the input line and set to a predetermined pressurecorresponding to a pressure of refrigerant needed to charge therefrigeration system; a high-pressure-side gauge for indicating pressureof the refrigerant entering a high-pressure-side of the pressureregulator; a low-pressure-side gauge for adjusting and monitoringpressure of the refrigerant leaving the pressure regulator; a sensor fordetecting a pressure of the vapor-phase refrigerant being introducedinto the refrigeration system of the vehicle from the input line; acontrol valve between the refrigerant source and the pressure regulator;and a controller connected to the control valve, the pressure regulator,and the sensor, wherein during a refrigeration charging operation, thecontroller is configured to close the control valve directly responsiveto a pressure of the refrigerant in the refrigeration system of thevehicle detected by the sensor reaching a predetermined pressure and toadjust the pressure regulator.
 4. A method of charging a refrigerationsystem of a vehicle with a vapor-phase refrigerant, comprising the stepsof: connecting a pressure sensor to the refrigeration system of thevehicle; predetermining a pressure of the vapor-phase refrigerant basedupon the refrigeration system of the vehicle being fully charged;setting a pressure regulator to the predetermined pressure; transferringvapor-phase refrigerant from a refrigerant source through an input line,and also through a control valve prior to the pressure regulator, to therefrigeration system of the vehicle; regulating the pressure of therefrigerant being introduced into the refrigeration system of thevehicle; indicating pressure of the refrigerant entering ahigh-pressure-side of the pressure regulator with a high-pressure-sidegauge; and adjusting and monitoring pressure of the refrigerant leavingthe pressure regulator with a low-pressure-side gauge electronicallycontrolled by a controller; measuring a pressure of the vapor-phaserefrigerant in the refrigeration system of the vehicle using thepressure sensor connected to the controller; and stopping the transferof vapor-phase refrigerant to the refrigeration system of the vehiclewith the control valve electronically controlled by the controllerdirectly responsive to the measured pressure of the vapor-phaserefrigerant in the refrigeration system of the vehicle equaling orexceeding the predetermined pressure.
 5. The method according to claim4, wherein the vapor-phase refrigerant is carbon dioxide.